Alluaudite Na₂Co₂Fe(PO₄)₃ as an electroactive material for sodium ion batteries

Essehli, R.,Belharouak, I.,Ben Yahia, H.,Maher, K.,Abouimrane, A.,Orayech, B.,Calder, S.,Zhou, X. L.,Zhou, Z.,Sun, Y-K. The Royal Society of Chemistry 2015 Dalton Transactions Vol.44 No.17

<P>The electroactive orthophosphate Na<SUB>2</SUB>Co<SUB>2</SUB>Fe(PO<SUB>4</SUB>)<SUB>3</SUB> was synthesized using a solid state reaction. Its crystal structure was solved using the combination of powder X-ray- and neutron-diffraction data. This material crystallizes according to the alluaudite structure (S.G. <I>C</I>2/<I>c</I>). The structure consists of edge sharing [MO<SUB>6</SUB>] octahedra (M = Fe, Co) resulting in chains parallel to [−101]. These chains are linked together <I>via</I> the [PO<SUB>4</SUB>] tetrahedra to form two distinct tunnels in which sodium cations are located. The electrochemical properties of Na<SUB>2</SUB>Co<SUB>2</SUB>Fe(PO<SUB>4</SUB>)<SUB>3</SUB> were evaluated by galvanostatic charge–discharge cycling. During the first discharge to 0.03 V, Na<SUB>2</SUB>Co<SUB>2</SUB>Fe(PO<SUB>4</SUB>)<SUB>3</SUB> delivers a specific capacity of 604 mA h g<SUP>−1</SUP>. This capacity is equivalent to the reaction of more than seven sodium ions per formula unit. Hence, this is a strong indication of a conversion-type reaction with the formation of metallic Fe and Co. The subsequent charge and discharge involved the reaction of fewer Na ions as expected for a conversion reaction. When discharged to 0.9 V, the material intercalated only one Na<SUP>+</SUP>-ion leading to the formation of a new phase Na<SUB>3</SUB>Co<SUB>2</SUB>Fe(PO<SUB>4</SUB>)<SUB>3</SUB>. This phase could then be cycled reversibly with an average voltage of 3.6 V <I>vs.</I> Na<SUP>+</SUP>/Na and a capacity of 110 mA h g<SUP>−1</SUP>. This result is in good agreement with the theoretical capacity expected from the extraction/insertion of two sodium atoms in Na<SUB>3</SUB>Co<SUB>2</SUB>Fe(PO<SUB>4</SUB>)<SUB>3</SUB>.</P> <P>Graphic Abstract</P><P>Na<SUB>2</SUB>Co<SUB>2</SUB>Fe(PO<SUB>4</SUB>)<SUB>3</SUB> crystallizes with the alluaudite-type structure (S.G. <I>C</I>2/<I>c</I>) and plays a dual anode/cathode behavior in sodium ion batteries. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5dt00971e'> </P>

Photovoltaic characterization of n-CdTe/p-CdMnTe/GaAs diluted magnetic diode

I.S. Yahia,F. Yakuphanoglu,S. Chusnutdinow,T. Wojtowicz,G. Karczewski 한국물리학회 2013 Current Applied Physics Vol.13 No.3

A CdTe/CdMnTe heterojunction magnetic diode for photovoltaic applications was fabricated by using molecular beam epitaxy (MBE). The ideality factor and the potential barrier height of the diode were determined to be 1.25 and 0.836 eV, respectively. Photovoltaic parameters of the studied device were determined at various illumination intensities. The highest open circuit voltage of the CdTe/CdMnTe heterostructure was equal to 0.56 V at the illumination intensity of 130 mW/cm2. The reverse current of the n-CdTe/p-CdMnTe/GaAs diode increases with the increasing illumination intensities. The obtained results suggest that n-CdTe/p-CdMnTe/GaAs diode can be used as a photodiode in photovoltaic and photodetector applications.

Tuning the physical properties of Sb-doped ZnO nanopowders toward elevated photosensing and photocatalytic activity

Kumari S. Senthil,Nirmala W.,Chidhambaram N.,Prabu M.,Ganesh V.,Yahia I. S. 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.4

This report outlines the photo sensing and photocatalytic properties of the Sb-doped ZnO nanopowders synthesized using the co-precipitation method. According to X-ray diffraction analyses, the produced nanopowders are polycrystalline and devoid of any secondary phase clusters. After antimony was added to the ZnO host matrix, a reduction in crystallite size was noticed. The distinct stretching vibrational modes (Zn–O and Sb–O) present in the produced nanopowders are validated using FTIR measurements. The bandgap shrinkage from 3.21 to 3.16 eV was obtained with the substitution of 5 wt% antimony in the ZnO matrix. In the case of Sb doped nanopowder samples, the reduction in ultraviolet band emission intensity was observed signifying the delayed photo-generated charge carriers recombination, which could favor the photo sensing and photocatalytic activity in ZnO. The photo sensing of the fabricated devices showed maximum responsivity (R), detectivity (D*), and external quantum efficiency (EQE) of 4.78 × 10–2 AW−1, 4.27 × 109 Jones and 11.1%, respectively for the 5% Sb-doped ZnO nanopowder. In addition, the 5% Sb-doped ZnO nanopowder photocatalysts reveal a superior degradation efficiency of 77% among other prepared photocatalysts.

Experimental Investigation of Convective Heat Transfer in a Narrow Rectangular Channel for Upward and Downward Flows

조대성,OMAR S. AL-YAHIA,RAGA’I M. ALTAMIMI,박종학,채희택 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.2

Heat transfer characteristics in a narrow rectangular channel are experimentally investigated for upward and downwardflows. The experimental data obtained are compared with existing data and predictions by many correlations. Based on theobservations, there are differences from others: (1) there are no different heat transfer characteristics between upward anddownward flows, (2) most of the existing correlations under-estimate heat transfer characteristics, and (3) existing correlationsdo not predict the high heat transfer in the entrance region for a wide range of Re. In addition, there are a few heat transfercorrelations applicable to narrow rectangular channels. Therefore, a new set of correlations is proposed with and withoutconsideration of the entrance region. Without consideration of the entrance region, heat transfer characteristics are expressedas a function of Re and Pr for turbulent flows, and as a function of Gz for laminar flows. The correlation proposed forturbulent and laminar flows has errors of ±18.25 and ±13.62%, respectively. With consideration of the entrance region, theheat transfer characteristics are expressed as a function of Re, Pr, and z* for both laminar and turbulent flows. The correlationfor turbulent and laminar flows has errors of ±19.5 and ±22.0%, respectively.

Low Cost Alcoholic Breath Sensor Based on SnO2 Modified with CNTs and Graphene

M. Morsy,I. S. Yahia,H. Y. Zahran,M. Ibrahim 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.73 No.10

In this work, SnO2 modified with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) separately and combined sensitized by using the co-precipitation method and their sensing behavior toward ethanol vapor at room temperature were investigated. An interdigitated electrode (IDE) gold substrate is very expensive compared to a uorine doped tin oxide (FTO) substrate; hence, we used the latter to reduce the fabrication cost. The structure and the morphology of the studied materials were characterized by using differential thermal analyses (DTA) and thermogravimetric analysis (TGA), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller surface area and Barrett-Joyner- Halenda (BJH) pore size measurements. The studied composites were subjected to ethanol in its gas phase at concentrations from 10 to 200 ppm. The present composites showed high-performance sensitivity for many reasons: the incorporation of SnO2 and CNTs which prevents the agglomeration of rGO sheets, the formation of a 3D mesopourus structure and an increase in the surface area. The decoration with rGO and CNTs led to more active sites, such as vacancies, which increased the adsorption of ethanol gas. In addition, the mesopore structure and the nano size of the SnO2 particles allowed an ecient diffusion of gases to the active sites. Based on these results, the present composites should be considered as ecient and low-cost sensors for alcohol.

EXPERIMENTAL INVESTIGATION OF CONVECTIVE HEAT TRANSFER IN A NARROW RECTANGULAR CHANNEL FOR UPWARD AND DOWNWARD FLOWS

Jo, Daeseong,Al-Yahia, Omar S.,Altamimi, Raga'i M.,Park, Jonghark,Chae, Heetaek Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.2

Heat transfer characteristics in a narrow rectangular channel are experimentally investigated for upward and downward flows. The experimental data obtained are compared with existing data and predictions by many correlations. Based on the observations, there are differences from others: (1) there are no different heat transfer characteristics between upward and downward flows, (2) most of the existing correlations under-estimate heat transfer characteristics, and (3) existing correlations do not predict the high heat transfer in the entrance region for a wide range of Re. In addition, there are a few heat transfer correlations applicable to narrow rectangular channels. Therefore, a new set of correlations is proposed with and without consideration of the entrance region. Without consideration of the entrance region, heat transfer characteristics are expressed as a function of Re and Pr for turbulent flows, and as a function of Gz for laminar flows. The correlation proposed for turbulent and laminar flows has errors of ${\pm}18.25$ and ${\pm}13.62%$, respectively. With consideration of the entrance region, the heat transfer characteristics are expressed as a function of Re, Pr, and $z^*$ for both laminar and turbulent flows. The correlation for turbulent and laminar flows has errors of ${\pm}19.5$ and ${\pm}22.0%$, respectively.

Analysis of the electrical properties of p-n GaAs homojunction under dc and ac fields

A.A.M.Farag,M. Fadel,I.S. Yahia 한국물리학회 2012 Current Applied Physics Vol.12 No.6

In this work, the n-type GaAs films were grown on p-type GaAs single crystalline substrate by metal organic chemical vapor deposition (MOCVD). The temperature dependence of the current densityevoltage (J-V) characteristics of n-GaAs/p-GaAs homojunction contacts were measured in the temperature range 293-413 K. These characteristics showed a rectifying behavior consistent with a potential barrier formed at the interface. The forward current densityevoltage characteristics under low voltage biasing were explained on the basis of thermionic emission mechanism. The high values of ideality factor (n) may be ascribed to the presence of an interfacial layer. Analysis of the experimental data under the reverse voltage biasing suggests a dominant mechanism was found to be a Schottky effect. The impedance properties and the alternating current (ac) conductivity of n-GaAs/p-GaAs homojunction were investigated as a function of frequency and temperature. The ac conductivity was found to obey the universal power law. The variation of the exponent s with the temperature suggested that the conduction mechanism is an overlapping large-polaron tunneling (OLPT) model associated with correlated barrier hopping (CBH) model at the higher temperature

Impacts of surface irregularity on vibration analysis of single-walled carbon nanotubes based on Donnell thin shell theory

Selim, Mahmoud M.,Althobaiti, Saad,Yahia, I.S.,Mohammed, Ibtisam M.O.,Hussin, Amira M.,Mohamed, Abdel-Baset A. Techno-Press 2022 Advances in nano research Vol.12 No.5

The present work is an attempt to study the vibration analysis of the single-walled carbon nanotubes (SWCNTs) under the effect of the surface irregularity using Donnell's model. The surface irregularity represented by the parabolic form. According to Donnell's model and three-dimensional elasticity theory, a novel governing equations and its solution are derived and matched with the case of no irregularity effects. To understand the reaction of the nanotube to the irregularity effects in terms of natural frequency, the numerical calculations are done. The results obtained could provide a better representation of the vibration behavior of an irregular single-walled carbon nanotube, where the aspect ratio (L/d) and surface irregularity all have a significant impact on the natural frequency of vibrating SWCNTs. Furthermore, the findings of surface irregularity effects on vibration SWCNT can be utilized to forecast and prevent the phenomena of resonance of single-walled carbon nanotubes.

Bimodal Approach for the Use of Co Doped Magnetite as MRI Contrast Agent and Potential Antitumor

Ahmed. A. G. El-Shahawy,Yasser GadelHak,H. Y. Zahran,I. S. Yahia,S. I. El-Dek 한국자기학회 2020 Journal of Magnetics Vol.25 No.4

Cobalt doped magnetite Co<SUP>2+</SUP> 0.1Fe<SUP>2+</SUP> 0.9Fe<SUP>3+</SUP> ₂O₄ nanocrystals were synthesized chemically using simple one step coprecipitation in the absence and presence of the magnetic field. The nanocrystals were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetization studies by vibrational spectroscopy magnetometer (VSM). The signal intensity of the prepared nanoparticles was measured by magnetic resonance imaging (MRI). The cytotoxicity of the two samples versus W138 normal lung cells and AS49 lung cancer cells was investigated by MTT assay, in vitro. The TEM images showed non-spherical and aggregated nanoparticles, heterogeneously dispersed with 100 nm average size. The XRD and selected area electron diffraction of the two samples revealed good crystallinity for both samples. The room temperature magnetization curves demonstrate the general ferrimagnetic trend with a clear difference in the coercivity and the remanence keeping the saturation magnetization nearly stable. The measured MR signal intensity was well-matched with the result of the M-H loops where the sample prepared in the absence of the field was a promising T2 contrast agent. Both samples have low cytotoxicity compared to Doxorubicin.